Hmm - tough one there, rhino, because in theory, he's not wrong. Using a unicompartmental is always a choice between options of hope and resignation. Hope that it will last a long time and resignation that you might as well opt for the full replacement and so preempt the possibility of revision.
Truth to tell, your surgeon is the best person to advise you. To my knowledge, all surgeons do unis as well as totals so you shouldn't need to worry on that score. And his opinion will be based upon the general condition of the entire joint and your weight based upon his expert knowledge and experience. There are certain signs a surgeon can pick up on - where the deterioration has occurred and the distribution of it.
However, you don't tell me your age or gender or what work you are involved in. All of this makes a difference. If you are a 55 year old housewife with average weight and with specific unicompartmental wear, I would have thought a uni was worth a go. You might be looking at revision eventually but probably not for 10-15 years if you are lucky.
I wish you the very best - do come back and let us know what your decision was and how you get on.